A dome camera is used as a surveillance camera or the like. In such a surveillance camera, a camera lens is covered by a dome cover, and the camera lens is protected by the dome cover. Also, a general surveillance camera includes a pan tilt function (a function of rotating a camera lens in a pan direction and a tilt direction) and a zoom function.
A conventional dome camera includes a hemispherical dome cover, and the center of rotation of a camera lens is arranged to be on the optical axis and to coincide with the center of the dome cover. It is known that a good image is obtained according to this arrangement.
However, according to the arrangement of the camera lens as described above, when capturing an image in a direction at a large tilt angle (a direction near the horizontal direction), vignetting occurs, and a good image is not obtained. Accordingly, a technique of offsetting the camera lens from the center of the dome cover in a zenith direction is conventionally proposed (for example, see Patent Literatures 1 and 2).
By offsetting the camera lens in the zenith direction of the dome cover, capturing of an image in a direction at a large tilt angle (a direction near the horizontal direction) is enabled without the vignetting occurring.
However, with a conventional dome camera, since the camera lens is offset from the center of the dome cover, aberration due to a lens effect of the dome cover occurs, and the image quality is deteriorated due to this aberration. That is, in the case of capturing an image in a direction at a large tilt angle (a direction near the horizontal direction), securing of a wide field of view and reduction in the image quality deterioration are in the relationship of tradeoff, and it is extremely difficult to achieve both of the two.